Ultrasonic vibrator for measurement apparatus and manufacturing method thereof

Abstract

To provide an ultrasonic vibrator for a measurement apparatus capable of widening a frequency band suitable for transmitting / receiving ultrasonic waves.SOLUTION: An ultrasonic vibrator 11 for a measurement apparatus comprises a housing container 21 which has a support plate 23, and a piezoelectric element 31 which has a substantially circular outer shape and is supported by the support plate 23. The piezoelectric element 31 is formed in a substantially acute triangle, in a planar view, of which one internal angle is 45° or smaller and the other two internal angles are 45° or larger. The piezoelectric element 31 includes a plurality of eight or more vibration parts 41 disposed in rotational symmetry while directing the internal angle of an acutest angle toward a center of the element. The piezoelectric element 31 is vibrated in a thickness direction A3 in a first frequency band and vibrated in a radial direction A4 in a second frequency band which is lower than the first frequency band.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic transducer for use in a measuring instrument that transmits and receives ultrasonic waves, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, fish finders that detect underwater fish schools by transmitting and receiving ultrasonic waves are well known. In this type of fish finder, ultrasonic transducers are used to transmit and receive ultrasonic waves, so that underwater conditions can be detected. The underwater detection results are displayed on a screen as an image.

[0003] By the way, ultrasonic transducers for fish finders usually use disc-shaped or annular piezoelectric elements, and are designed to transmit and receive ultrasonic waves of two different frequencies, such as 200 kHz for thickness vibration and 50 kHz for radial vibration, with one transducer. However, this type of piezoelectric element has a narrow frequency band for each ultrasonic wave. In recent years, the number of ships equipped with similar fish finders has increased, making interference with other ships more likely to occur. In order to avoid interference, ultrasonic waves can be transmitted and received by changing the driving frequency used by nearby ships, but if the frequency band is narrow, the options for changing the frequency are limited. For this reason, it is necessary to use ultrasonic transducers with a wide ultrasonic frequency band.

[0004] As a method for making ultrasonic waves broadband, as shown in Fig. 21 and Fig. 22, a piezoelectric element 192 constituting an ultrasonic transducer 191 is formed with a plurality of grooves 193 extending in the same direction, and a plurality of vibration parts 194 are disposed through the grooves 193 (see, for example, Patent Document 1). In this way, each vibration part 194 is easily deformed in the thickness direction of the piezoelectric element 192. As a result, the piezoelectric element 192 is easily vibrated in the thickness direction over the entire range, so that the electromechanical coupling coefficient is increased and the frequency band is also widened. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-213666 A (paragraph

[0023] , Figs. 1, 3, 4A, etc.) Summary of the Invention [Problem to be solved by the invention]

[0006] However, since Patent Document 1 is a technology that makes it easier for the piezoelectric element 192 to vibrate mainly in the thickness direction, it is difficult to say that a frequency band suitable for transmitting and receiving ultrasonic waves is sufficiently obtained. Therefore, there is a demand for a wider frequency band of ultrasonic waves. In addition, in order to obtain a wide-band ultrasonic transducer, there is also a demand for reducing waste of materials during manufacturing as much as possible and increasing production efficiency during manufacturing.

[0007] The present invention has been made in consideration of the above problems, and its object is to provide an ultrasonic transducer for measuring instruments that can widen the frequency band suitable for transmitting and receiving ultrasonic waves, and a method for manufacturing the same. [Means for solving the problem]

[0008] In order to solve the above problem, the invention described in claim 1 provides an ultrasonic transducer for a measuring instrument that transmits and receives ultrasonic waves, comprising a housing container having a support, and a piezoelectric element having an approximately circular outer shape and supported by the support, the piezoelectric element including eight or more vibrating parts that form an approximately acute triangle shape in a planar view with one interior angle of 45° or less and the other two interior angles of 45° or more, and that are arranged rotationally symmetrically with the acutest interior angle toward the center of the element, and the piezoelectric element vibrates in the thickness direction in a first frequency band and vibrates in the radial direction in a second frequency band lower than the first frequency band.

[0009] Therefore, according to the invention described in claim 1, since the piezoelectric element includes a plurality of vibration parts divided by the grooves, each vibration part is easily deformed in the thickness direction. As a result, the piezoelectric element vibrates in the thickness direction over the entire area, and the electromechanical coupling coefficient is high. Therefore, the transmission and reception sensitivity of the first frequency band, which is the frequency band of the thickness direction vibration, is high, and the range of the first frequency band is also wide. In addition, each vibration part constituting the piezoelectric element is approximately an acute triangle shape in a plan view with one interior angle of 45° or less and the other two interior angles of 45° or more. In other words, since it is easy to become a vibration part that is elongated in the radial direction, when driven at the resonant frequency of the radial vibration, the vibration part vibrates with a large amplitude along the extension direction of the interior angle of 45° or less. As a result, the transmission and reception sensitivity of the second frequency band, which is the frequency band of the radial vibration of the vibration part, is high. From the above, it is possible to transmit and receive with high sensitivity in both the thickness direction vibration and the radial direction vibration.

[0010] The interior angle of 45° or less in the approximately acute triangle shape (hereinafter simply referred to as the "acutest angle") is preferably 30° or less, and more preferably 20° or less. The reason for this is that by setting the acutest angle in this range, it becomes easier to obtain a vibrating part with a slender planar shape that is advantageous for radial vibration.

[0011] Here, "approximately acute triangle shape" includes right triangle shape and isosceles triangle shape. Even if at least one of the interior angles of a right triangle is slightly chamfered, if it is almost a right triangle shape when viewed from the beginning (i.e., if it is almost a right triangle shape), it is considered to be included in "approximately acute triangle shape". Similarly, even if at least one of the interior angles of an isosceles triangle is slightly chamfered, if it is almost an isosceles triangle shape when viewed from the beginning (i.e., if it is almost an isosceles triangle shape), it is also considered to be included in "approximately acute triangle shape".

[0012] It should be noted that a piezoelectric element having a "substantially circular outer shape" includes not only a piezoelectric element having a circular outer shape, but also a piezoelectric element having an elliptical outer shape, a piezoelectric element having an oval outer shape, and the like.

[0013] The support may be a support plate having a flat surface (claim 2), but may also be a support plate having a surface that is not flat but is generally convex or concave and has an inclined surface. With this configuration, it is possible to set a directivity angle different from that in the case where the piezoelectric element is supported on a support plate having a flat surface. The support may have a shape other than a plate shape (for example, a rod shape or a protrusion shape).

[0014] For example, the support plate may have a surface shape equivalent to the pyramidal surface of an approximately polygonal pyramid or an approximately frustum of a polygonal pyramid, and may be generally convex on the outer surface side (Claim 3). With this configuration, each vibration part can be stably supported on the support plate while being held at a desired angle, and the directional angle can be made wider than when the piezoelectric element is supported on a support plate having a flat surface shape. Alternatively, the support plate may have a surface shape equivalent to the pyramidal surface of an approximately polygonal pyramid or an approximately frustum of a polygonal pyramid, and may be generally concave on the outer surface side (Claim 4). With this configuration, each vibration part can be stably supported on the support plate while being held at a desired angle, and may be generally concave on the outer surface side.

[0015] In addition, when the support plate has a surface shape corresponding to the pyramidal surface of an approximately polygonal pyramid or an approximately polygonal frustum, and the outer surface side of the support plate is generally convex or concave, the multiple vibration parts may be supported by multiple constituent surfaces that constitute the pyramidal surface (claim 5). With this configuration, the multiple divided vibration parts can be stably supported on the support plate while being held at a desired angle.

[0016] The invention described in claim 6 is characterized in that the thickness of the vibrating part is greater than the width of the vibrating part, and the length of the vibrating part in the centrifugal direction is three times or more the thickness of the vibrating part in any one of claims 1 to 4. Therefore, according to the invention described in claim 6, the vibrating part has an elongated shape that easily vibrates in the radial direction, which increases the electromechanical coupling coefficient and reliably widens the range of the second frequency band, which is the frequency band of radial vibration.

[0017] The invention as set forth in claim 7 is characterized in that in any one of claims 1 to 4, a portion of the vibrating part corresponding to the interior angle that is the acutest angle has a chamfered shape. Therefore, according to the invention as set forth in claim 7, by chamfering the acutest angle of the vibrating part, the sharpness of the tip of the acutest angle is eliminated, and chipping of the vibrating part can be prevented.

[0018] The invention described in claim 8 is based on any one of claims 1 to 4, and further comprises an acoustic matching layer bonded to the radiation surface of the vibration section, the area of ​​the bonded region of the acoustic matching layer being set smaller than the area of ​​the radiation surface, a step portion being formed in a portion of the outer edge of the radiation surface where the acoustic matching layer is not present, and an electrode being formed in the step portion. Therefore, according to the invention described in claim 8, wiring can be bonded more stably to the electrode formed in the step portion than to the electrode on the side surface of the vibration section.

[0019] The adjacent vibration parts may be bonded and fixed to each other, for example, by a filler or soundproofing material often used in ultrasonic vibrators. The means for bonding and fixing the adjacent vibration parts may be a soundproofing sheet with double-sided tape (claim 9). The double-sided tape of the soundproofing sheet can be attached to the side of the vibration parts, so when this is used, the vibration parts can be bonded and fixed to each other reliably and relatively easily with each vibration part correctly positioned.

[0020] The invention described in claim 10 relates to a method for manufacturing an ultrasonic transducer comprising: a housing container having a support; and a piezoelectric element having a substantially circular outer shape and supported by the support, the piezoelectric element being configured to include eight or more vibration parts that are arranged in a rotational symmetry manner with the acutest interior angle toward the center of the element, forming a substantially acute triangle shape in a plan view with one interior angle of 45° or less and two other interior angles of 45° or more, the piezoelectric element vibrating in a thickness direction in a first frequency band and vibrating in a radial direction in a second frequency band lower than the first frequency band, the method comprising the steps of: The gist of the invention is a method for manufacturing an ultrasonic transducer for a measuring instrument, the method including: a preparation step of preparing a ceramic sintered body; a cutting step of cutting the ceramic sintered body at equal pitches along a first direction and at equal pitches along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming a plurality of the vibration parts having an approximately acute triangle shape; and a vibration part arrangement step of forming the piezoelectric element by using eight or more of the obtained vibration parts and arranging the vibration parts so that the acutest interior angle is rotationally symmetrical toward the center of the element.

[0021] The invention described in claim 11 is based on claim 10, and is characterized in that the multiple vibration parts are approximately right-angled triangular in plan view, and in the cutting process, the ceramic sintered body is cut at equal pitches along the first direction parallel to a short side of the ceramic sintered body, and cut at equal pitches along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming the multiple vibration parts having approximately right-angled triangular shapes.

[0022] The invention described in claim 12 is based on claim 10, and is characterized in that the multiple vibration parts are approximately isosceles triangular in plan view, and in the cutting process, the ceramic sintered body is cut at equal pitches along the first direction that forms an angle of half the acutest interior angle with respect to a short side of the ceramic sintered body, and cut at equal pitches along a second direction that forms an angle equal to the acutest interior angle with the first direction, thereby forming the multiple vibration parts having an approximately isosceles triangular shape.

[0023] The invention described in claim 13 includes a housing container having a support, and a piezoelectric element having a substantially circular outer shape and supported by the support, the piezoelectric element being configured to include eight or more vibration parts that form a substantially acute triangle shape in a plan view with one interior angle of 45° or less and two other interior angles of 45° or more, and are arranged rotationally symmetrically with the acutest interior angle toward the center of the element, an acoustic matching layer is bonded to a radiation surface of the vibration parts, and an area of ​​a bonding region of the acoustic matching layer is set to be smaller than an area of ​​the radiation surface, a step part is formed at a location on the outer edge of the radiation surface where the acoustic matching layer is not present, and an electrode is formed on the step part, and the piezoelectric element vibrates in a thickness direction in a first frequency band and vibrates in a radial direction in a second frequency band lower than the first frequency band. The gist of the present invention is a method for manufacturing an ultrasonic transducer for use in measuring instruments, comprising the steps of: preparing a rectangular, flat ceramic sintered body having a rectangular, flat acoustic matching layer bonded to one side of the ceramic sintered body; cutting the ceramic sintered body at equal pitches along a first direction and at equal pitches along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming a plurality of vibration parts each having an approximately acute triangle shape; a vibration part arrangement step using eight or more of the obtained vibration parts and arranging the vibration parts so that the acutest interior angle is rotationally symmetrical toward the center of the element, thereby forming the piezoelectric element; and a wiring connection step connecting wiring to the electrode formed on the step portion of the vibration part. Effect of the Invention

[0024] As described above in detail, according to the inventions recited in claims 1 to 9, it is possible to obtain an ultrasonic transducer for a measuring device capable of widening the frequency band suitable for transmitting and receiving ultrasonic waves. In particular, according to the inventions recited in claims 3 to 5, it is possible to provide a wide or narrow beam angle. Furthermore, according to the inventions recited in claims 10 to 13, it is possible to provide a method for relatively simply and efficiently manufacturing the above-mentioned wideband ultrasonic transducer while reducing waste of materials. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an ultrasonic transducer according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view showing a piezoelectric element in the ultrasonic transducer according to the first embodiment. [Diagram 3] FIG. 2 is a perspective view showing a vibration part that constitutes the piezoelectric element. [Figure 4] FIG. 13 is a perspective view showing a piezoelectric element in an ultrasonic transducer according to a modified example of the first embodiment. [Diagram 5] FIG. 13 is a perspective view showing a vibration portion constituting a piezoelectric element according to a modified example. [Figure 6] FIG. 2 is a plan view showing a state in which the piezoelectric element of the first embodiment is supported by a support plate. [Figure 7] 4 is a graph showing the relationship between frequency and impedance for an embodiment. [Figure 8] 4 is a graph showing the relationship between frequency and transmission / reception sensitivity for the embodiment and comparative examples 1 and 2. [Figure 9] FIG. 6 is a schematic cross-sectional view showing an ultrasonic transducer according to a second embodiment. [Figure 10] FIG. 11 is a perspective view showing a piezoelectric element in an ultrasonic transducer according to a second embodiment. [Figure 11] 6(a) to (c) are schematic diagrams showing a procedure for producing a piezoelectric element in an ultrasonic transducer according to a second embodiment, and (d) is a perspective view showing a piezoelectric element obtained through the procedure. FIG. [Figure 12] FIG. 11 is a perspective view showing a piezoelectric element in an ultrasonic transducer according to a third embodiment. [Figure 13] 13(a) to (c) are schematic diagrams showing a procedure for producing a piezoelectric element in an ultrasonic transducer according to a third embodiment, and (d) is a perspective view showing a piezoelectric element obtained through the procedure. FIG. [Figure 14] FIG. 13 is a schematic cross-sectional view showing an ultrasonic transducer according to a fourth embodiment. [Figure 15] FIG. 13 is a perspective view showing a piezoelectric element in an ultrasonic transducer according to a fourth embodiment. [Figure 16] FIG. 13 is a plan view showing a state in which the piezoelectric element of the fourth embodiment is supported by a support plate. [Figure 17]FIG. 13 is a schematic cross-sectional view showing an ultrasonic transducer according to a fifth embodiment. [Figure 18] FIG. 13 is a perspective view showing a piezoelectric element in an ultrasonic transducer according to a fifth embodiment. [Figure 19] FIG. 11 is a perspective view showing a state in which a soundproof sheet is disposed between vibration portions of a piezoelectric element having a tape-attached structure in another embodiment. [Figure 20] FIG. 11 is a schematic cross-sectional view showing an ultrasonic transducer according to another embodiment. [Figure 21] FIG. 1 is a plan view showing a main portion of a piezoelectric element according to a conventional technique. [Figure 22] FIG. 11 is a cross-sectional view showing a vibrating portion in the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] [First embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic transducer for use in a measuring instrument according to a first embodiment of the present invention will now be described in detail with reference to FIGS.

[0027] As shown in Figs. 1 and 2, the ultrasonic transducer 11 is an ultrasonic transducer for use in a measuring instrument, and in this embodiment is embodied as an ultrasonic transducer used in a fish finder.

[0028] As shown in FIG. 1, the ultrasonic transducer 11 includes a housing container 21, a piezoelectric element 31, and the like. The housing container 21 is a container for accommodating the piezoelectric element 31, and is composed of a container body 22 and a support plate 23. The container body 22 is formed in a bottomed cylindrical shape having an opening on the front side 26 using a resin material such as ABS resin. The support plate 23 as a support is arranged and fixed to the front side 26 of the container body 22 to close the opening. As shown in FIG. 6, the support plate 23 of this embodiment is a member having the same diameter as the opening of the container body 22 and a circular shape in a plan view, and has a flat surface shape without any particular unevenness. The material for forming the support plate 23 is not particularly limited as long as it has mechanical strength capable of supporting the piezoelectric element 31 and is capable of transmitting ultrasonic waves, but a resin material such as ABS resin is used.

[0029] As shown in Figs. 1, 2 and 6, the piezoelectric element 31 is a ceramic plate having a substantially circular outer shape, and is formed, for example, using lead zirconate titanate (PZT) which is a piezoelectric ceramic. The outer diameter of the piezoelectric element 31 is slightly smaller than that of the circular support plate 23, and therefore the area of ​​the support plate 23 is slightly larger than that of the piezoelectric element 31. The piezoelectric element 31 has a first surface 31a which is an ultrasonic wave emitting surface and a second surface 31b on the opposite side. One side of the acoustic matching layer 32 is bonded to the first surface 31a of the piezoelectric element 31 using an adhesive, and the other side of the acoustic matching layer 32 is bonded to the inner surface 23a of the support plate 23 using an adhesive. That is, the piezoelectric element 31 and the support plate 23 are bonded via the acoustic matching layer 32. A front electrode 33 is formed on the first surface 31a of the piezoelectric element 31, and a back electrode 34 is formed on the second surface 31b of the piezoelectric element 31. By applying a voltage between the front electrode 33 and the rear electrode 34, the piezoelectric element 31 is polarized in the thickness direction.

[0030] The piezoelectric element 31 has a generally acute triangle shape in plan view with one interior angle of 45° or less and the other two interior angles of 45° or more. Specifically, the piezoelectric element 31 of this embodiment has a narrow isosceles triangle shape in plan view (see FIGS. 2 and 3). One interior angle, which is the acutest angle, is 15°, and the other two interior angles are 82.5°.

[0031] Moreover, the piezoelectric element 31 is configured to include eight or more vibration parts 41 arranged in rotational symmetry with the acutest interior angle facing the element center, and in this embodiment, includes 24 vibration parts 41. The grooves 36 communicate with each other at the center of the piezoelectric element 31 and extend radially. The 24 vibration parts 41 are not connected to each other, but are completely separated from each other by the grooves 36. The grooves 36 are arranged at equal angular intervals (15° intervals in this embodiment) with the center of the piezoelectric element 31 as the reference. In other words, the intersections of the grooves 36 coincide with the center. The widths of the grooves 36 are equal to each other.

[0032] Each vibration part 41, which is an elongated isosceles triangle in plan view, has the same size and shape. Specifically, as shown in Fig. 3 etc., a main surface 42 of the vibration part 41 is composed of three sides 43, 44, 45. The shortest side 43, which is located on the outer periphery side of the piezoelectric element 31, is straight, and the remaining two sides 44, 45 are of equal length and straight. The outer surface of each vibration part 41 constitutes a part of the outer periphery of the piezoelectric element 31.

[0033] The thickness L1, width L2, and radial length L3 (here, the length of sides 44 and 45) of each vibrating part 41 forming an elongated isosceles triangle shape are not particularly limited and can be set arbitrarily, but the thickness L1 is preferably set to be larger than the width L2, and for example, the thickness L1 is set to be 1.1 times or more, and further 1.1 times or more and 3.0 times or less, of the width L2. The radial length L3 is preferably set to be twice or more, and more preferably three times or more, of the thickness L1 and the width L2. Specifically, in this embodiment, the thickness L1 is set to about 1.5 to 2.0 times the width L2, and the radial length L3 is set to about 3.0 to 3.5 times the thickness L1.

[0034] 4 and 5 show a piezoelectric element 31A according to a modification of this embodiment. The piezoelectric element 31A according to the modification has an elongated, approximately right-angled triangular shape in plan view. One of the interior angles, which is the most acute angle, is 15°, and the other two interior angles are 75° and 90°. However, the acute angle portion 72 arranged on the central side of the piezoelectric element 31A in each vibration part 41A is chamfered. Therefore, the sharpness of the tip of the acute angle portion 72 in each vibration part 41A is eliminated, and chipping of each vibration part 41A can be prevented.

[0035] Each vibration part 41A, which is an elongated right-angled triangle in plan view, has the same size and shape. Specifically, as shown in FIG. 5 and other figures, the main surface 42 of the vibration part 41A is composed of three sides 43a, 44a, and 45a. The shortest side 43a, which is located on the outer periphery side of the piezoelectric element 31A, is linear. Of the remaining two sides 44a and 45a, side 44a is the longest linear oblique side, and side 45a is a slightly shorter linear side. Side 43a and side 45a intersect at a right angle.

[0036] The thickness L1, width L2, and radial length L3 (here, the length of the side 44a, which is the hypotenuse) of each vibrating part 41A forming an elongated right-angled triangle are not particularly limited and can be set arbitrarily, but the thickness L1 is preferably set to be larger than the width L2, and for example, the thickness L1 is set to be 1.1 times or more, and further 1.1 times or more and 3.0 times or less, of the width L2. The radial length L3 is preferably set to be twice or more, and more preferably three times or more, of the thickness L1 and the width L2. Specifically, in this embodiment, the thickness L1 is set to about 1.5 to 2.0 times the width L2, and the radial length L3 is set to about 3.0 to 3.5 times the thickness L1.

[0037] 1, a conductive metal foil (not shown) (e.g., copper foil, brass foil, aluminum foil, etc.) is attached to the multiple back electrodes 34 formed on the upper main surface 42 of each of the vibration parts 41, 41A so as to bridge them. The metal foil is attached to each back electrode 34 by a conductive metal such as solder or a conductive adhesive containing a conventionally known conductive filler. This metal foil functions as a common electrode on the upper main surface 42 of each of the vibration parts 41, 41A.

[0038] A first lead wire 51 of a wiring cable 53 is connected to the front electrode 33, and a second lead wire 52 of the wiring cable 53 is connected to the back electrode 34. The first lead wire 51 is connected to a side terminal (not shown) extending outward from the front electrode 33 by soldering or the like. The second lead wire 52 is connected to any one of the multiple back electrodes 34 by soldering or the like. The wiring cable 53 bundling the first lead wire 51 and the second lead wire 52 is drawn out of the housing container 21 through a cable insertion hole 54 provided in the upper center of the container body 22. Note that, in addition to connecting the first lead wire 51 to the side terminal, another connection method may be adopted. For example, a metal foil (not shown) such as a copper foil may be attached to the upper main surface 42 of the front electrode 33, and the first lead wire 51 may be soldered to the metal foil.

[0039] Moreover, a sheet-like backing material 61 (soundproofing material or acoustic attenuation material) is attached to the second surface 31b side of the piezoelectric elements 31, 31A (i.e., the upper main surface 42 side of each vibrating portion 41, 41A). The backing material 61 is for suppressing reverberation, and is also attached to the inner peripheral surface of the housing container 21. As such a backing material 61, a material in which particles or fibers made of metal or ceramic are contained in a resin material or rubber, or a material in which pores are dispersed in a resin material (such as a urethane sponge material) can be used.

[0040] Next, the operation of this ultrasonic transducer 11 will be described.

[0041] First, the power supply of the fish finder is turned on to operate a control device (not shown) and output a high-frequency signal to the ultrasonic transducer 11, thereby vibrating the ultrasonic transducer 11. At this time, each vibration part 41 of the piezoelectric element 31 and each vibration part 41A of the piezoelectric element 31A repeatedly contract and expand in a predetermined direction. For example, when the vibration parts 41 and 41A contract in the thickness direction A3, the vibration parts 41 and 41A deform so as to expand in the width direction (i.e., in the direction of the arrow A1 in Figs. 3 and 5). Conversely, when the vibration parts 41 and 41A expand in the thickness direction A3, the vibration parts 41 and 41A deform so as to contract in the width direction (i.e., in the direction of the arrow A2 in Figs. 3 and 5). As a result, the piezoelectric elements 31 and 31A vibrate, and ultrasonic waves are irradiated (transmitted) from the ultrasonic transducer 11 into the water. Then, when the ultrasonic waves reach a detection target such as a school of fish and are reflected, the reflected waves of the ultrasonic waves that have returned are received by the ultrasonic transducer 11. The reflected ultrasonic wave received by the ultrasonic transducer 11 is converted into a received signal and input to a control device, where the detected object is visualized through predetermined signal processing.

[0042] Next, an example of a method for manufacturing the ultrasonic transducer 11 will be described, but it goes without saying that the ultrasonic transducer 11 may be manufactured by a method other than this example.

[0043] For example, when manufacturing an ultrasonic transducer 11 using the piezoelectric element 31 of FIG. 2, first, 24 piezoelectric element pieces (i.e., vibration parts 41 with acoustic matching layers 32) each having an elongated isosceles triangle shape are prepared. Metal layers that become the front electrode 33 and the back electrode 34 are formed on both main surfaces 42 of the vibration parts 41 of the piezoelectric element pieces. Next, the 24 piezoelectric element pieces are supported on the inner surface 23a side of the support plate 23. Specifically, as shown in FIG. 6, the vibration parts 41 with the acoustic matching layers 32 are arranged on the inner surface 23a of the support plate 23 with the groove parts 36 between them. At this time, the groove parts 36 are arranged so that they are mutually connected at the center of the piezoelectric element 31 and the support plate 23 and extend radially. In this arrangement, each vibration part 41 is adhesively fixed to the inner surface 23a of the support plate 23 via the acoustic matching layers 32. Next, the first lead wire 51 and the second lead wire 52 are soldered to the front electrode 33 and the back electrode 34 of the piezoelectric element 31, respectively. Then, the wiring cable 53 is pulled out of the housing 21 through the cable insertion hole 54, and the support plate 23 is placed and fixed on the front side 26 of the housing body 22. As a result, the opening of the housing body 22 is closed, and the piezoelectric element 31 is housed in the space within the housing 21. Thereafter, the filler 38 is filled through a hole (not shown) provided in the housing 21, and the space is filled with the filler 38 and molded integrally. In this manner, the ultrasonic transducer 11 is completed.

[0044] Therefore, according to this embodiment, the following effects can be obtained.

[0045] (1) In the ultrasonic transducer 11 of this embodiment, the piezoelectric elements 31, 31A are composed of a plurality of vibration parts 41, 41A divided by the grooves 36, so that each vibration part 41, 41A is easily deformed in the thickness direction A3. As a result, the piezoelectric elements 31, 31A vibrate in the thickness direction A3 over the entire area, and the electromechanical coupling coefficient is increased. Therefore, the transmission and reception sensitivity of the first frequency band, which is the frequency band of the thickness direction vibration, is increased, and the range of the first frequency band is also widened. In addition, each vibration part 41, 41A constituting the piezoelectric elements 31, 31A is substantially an acute triangle shape in a plan view, with one interior angle being 45° or less and the other two interior angles being 45° or more. In other words, since the vibration parts 41, 41A are easily elongated in the radial direction, when driven at the resonant frequency of the radial vibration, the vibration part vibrates with a large amplitude in the direction in which the interior angle of 45° or less extends (i.e., A4). As a result, the transmission / reception sensitivity is increased in the second frequency band, which is the frequency band of the radial vibration of the vibrating parts 41 and 41A. From the above, it is possible to transmit and receive with high sensitivity in both the thickness direction vibration and the radial direction vibration.

[0046] (2) The piezoelectric element 31 of the present embodiment and the piezoelectric element 31A of the modified example thereof not only vibrate in the thickness direction A3 in the first frequency band, but also vibrate in the radial direction A4 in a frequency band different from the first frequency band, specifically, in the second frequency band lower than the first frequency band. Therefore, by switching between the first frequency band (for example, around 200 kHz) vibrating in the thickness direction A3 and the second frequency band (for example, around 50 kHz) vibrating in the radial direction A4 and driving the ultrasonic transducer 11, it becomes possible to transmit and receive ultrasonic waves in each frequency band. In addition, by simply providing one ultrasonic transducer 11 in the fish finder, it becomes possible to transmit and receive ultrasonic waves in two frequency bands, thereby making it possible to reduce the weight, size, and cost of the device.

[0047] When the ultrasonic transducer 11 is driven in the second frequency band (low frequency drive), it is less prone to attenuation compared to high frequency, allowing for deeper detection, and has the advantage of a wide beam angle, but the resolution of the received signal (reflected wave) is reduced. On the other hand, when the ultrasonic transducer 11 is driven in the first frequency band (high frequency drive), it is more prone to attenuation and the detection depth is shallower, but it is possible to perform detection with high resolution and a narrow beam angle. In this way, since it is possible to drive one ultrasonic transducer 11 by switching the frequency, it becomes possible to select detection according to the situation.

[0048] (3) The piezoelectric element 31 of this embodiment and the piezoelectric element 31A of the modified example thereof are composed of 24 divided vibration parts 41, 41A of equal size and shape. Therefore, the width L2 of each vibration part 41, 41A is small, and each vibration part 41, 41A has a shape that easily vibrates in the thickness direction A3. In other words, by making the piezoelectric elements 31, 31A have a shape that easily vibrates in the thickness direction A3, it is possible to increase the electromechanical coupling coefficient, increase the sensitivity in the first frequency band, which is the frequency band of thickness direction vibration, and widen the band.

[0049] (4) In this embodiment, the thickness L1 of the vibrating parts 41, 41A is greater than the width L2, and the radial length L3 is three or more times the thickness L1. Therefore, the vibrating parts 41, 41A have an elongated shape that easily vibrates in the radial direction A4, which increases the electromechanical coupling coefficient and reliably widens the range of the second frequency band, which is the frequency band of radial vibration.

[0050] [Evaluation of ultrasonic transducers] The evaluation method and results of the ultrasonic transducer 11 will be described below.

[0051] Here, the impedance of the vibration part 41 was measured for the piezoelectric element 31 (outer diameter 50 mm, thickness 7.2 mm) of this embodiment. Specifically, the measurement sample was measured while sweeping the frequency between 30 kHz and 300 kHz using an impedance analyzer. As a result, it was confirmed that the resonance region (valley region) of the radial vibration of the vibration part 41 was near 70 kHz, and the resonance region of the thickness direction vibration of the vibration part 41 was near 170 kHz (see FIG. 7). Therefore, it was confirmed that the vibration part 41 vibrated in the radial direction at a frequency lower than the frequency when vibrating in the thickness direction A3 in this measurement sample. It was also confirmed that the displacement amount in the radial vibration increased toward both ends (center and outer periphery) of the vibration part 41, and the displacement amount in the thickness direction vibration increased toward the front side and back side of the intermediate part.

[0052] Next, in addition to the piezoelectric element 31 (outer diameter 50 mm, thickness 7.2 mm) of this embodiment, two different types of piezoelectric elements 31 were produced. One of them had a plurality of grooves 36 extending in one direction formed on the piezoelectric element 31 having a circular outer shape, thereby forming a plurality of band-shaped vibration parts. The other was a piezoelectric element 31 having a circular outer shape without the grooves 36 formed. Then, using these piezoelectric elements 31, ultrasonic transducers 11 were prototyped (see FIG. 8). Specifically, the ultrasonic transducer 11 formed using the piezoelectric element 31 of this embodiment having a vibration part 41 in the shape of an elongated isosceles triangle was designated as Sample 1 (Example). The ultrasonic transducer 11 formed using the piezoelectric element 31 having a band-shaped vibration part was designated as Sample 2 (Comparative Example 1). The ultrasonic transducer 11 formed using the undivided piezoelectric element 31 was designated as Sample 3 (Comparative Example 2).

[0053] Then, the transmission and reception sensitivity of the ultrasonic transducer 11 was calculated for these measurement samples (samples 1 to 3). Specifically, the ultrasonic wave emitting surface of the ultrasonic transducer 11 was immersed in water, and ultrasonic waves were irradiated perpendicularly to a SUS plate located 170 mm away from the ultrasonic wave emitting surface. The ultrasonic waves (reflected waves) reflected by the SUS plate were received by the ultrasonic transducer 11, and voltage signals were generated at both ends of the ultrasonic transducer 11. At this time, the voltage amplitudes at the time of transmission and reception of the ultrasonic transducer 11 were measured by an oscilloscope, and the transmission and reception sensitivity was calculated by performing frequency component analysis and calculation of both the transmission voltage waveform and the reception voltage waveform. The transmission and reception sensitivity is the ratio of the reception voltage amplitude Vr to the transmission voltage amplitude Vs, and is calculated from the formula 20×log(Vr / Vs). The graph in FIG. 8 shows the relationship between the frequency and the transmission and reception sensitivity in samples 1 to 3.

[0054] As a result, it was confirmed that sample 1 (Example) vibrates in the thickness direction in the first frequency band where the transmission / reception sensitivity is at its peak at 210 kHz, and vibrates in the radial direction of the vibrating part in the second frequency band where the transmission / reception sensitivity is at its peak at 80 kHz, which is lower than the first frequency band. It was also confirmed that the range in which the transmission / reception sensitivity is, for example, -33 dB or more is around 135 kHz to 325 kHz in the first frequency band, and around 80 kHz to 90 kHz in the second frequency band. From the above, it was confirmed that both the first frequency band and the second frequency band of sample 1 are suitable for transmitting and receiving ultrasonic waves. It was also confirmed that when the grooves 36 are formed radially, the ultrasonic transducer has a wide band around 200 kHz, but a narrow band around 80 kHz.

[0055] On the other hand, in sample 2 (comparative example 1), it was confirmed that the transmission / reception sensitivity was vibrated in the thickness direction in a frequency band where the transmission / reception sensitivity peaked at 220 kHz. It was also confirmed that the range where the transmission / reception sensitivity was, for example, -33 dB or more was around 140 kHz to 340 kHz in the frequency band where the peak was 220 kHz. In addition, no peak in the radial vibration was observed in sample 2. As described above, it was confirmed that sample 2, which is comparative example 1, had a wide band in the thickness direction vibration, but the transmission / reception sensitivity due to the longitudinal vibration of the notch (groove) was weak. In contrast, it was confirmed that sample 1, which is an embodiment, had the same transmission / reception sensitivity and band characteristics in the thickness direction as sample 2, and also enabled transmission / reception at low frequencies due to the radial vibration of the vibration part 41.

[0056] In addition, it was confirmed that Sample 3 (Comparative Example 2) vibrates in the thickness direction in the frequency band where the transmission and reception sensitivity peaks at 205 kHz, and vibrates in the radial direction (diameter direction) in the frequency band where the transmission and reception sensitivity peaks at 50 kHz. It was also confirmed that the range where the transmission and reception sensitivity is, for example, -33 dB or more is around 195 kHz to 230 kHz in the first frequency band, and around 45 kHz to 55 kHz in the second frequency band. Sample 3, which is Comparative Example 2, is a transducer for fish finders that switches between two frequencies of 50 kHz and 200 kHz and is widely used in the market. On the other hand, Sample 1, which is an embodiment, has higher sensitivity and wider bandwidth than Sample 3 in the thickness direction vibration around 200 kHz, and also has the same transmission and reception sensitivity of low-frequency radial vibration as Sample 3, and it was found that it can be used in both frequency bands like Sample 3.

[0057] [Second embodiment] An ultrasonic transducer 11A according to a second embodiment of the present invention will be described below with reference to Figures 9 to 11. Here, the description will focus on the parts that are different from the first embodiment, and the same parts will be given the same reference numbers and detailed descriptions will be omitted.

[0058] As shown in FIG. 9, the piezoelectric element 31B in the ultrasonic transducer 11A of the second embodiment is a ceramic plate-like object having a substantially circular outer shape, and includes a plurality of vibration parts 41B that are elongated and substantially isosceles triangular in plan view. However, while the piezoelectric element 31 of the first embodiment includes 24 vibration parts 41, the piezoelectric element 31B here includes 18 vibration parts 41B. Specifically, in the vibration part 41B of this embodiment, one interior angle that is the most acute angle is 20°, and the other two interior angles are 80°. As shown in FIG. 9 and FIG. 10, the interior angles (acute angle parts 72) that are the most acute angles in each vibration part 41B are located on the central side of the piezoelectric element 31B, and are all chamfered to prevent chipping.

[0059] Moreover, an acoustic matching layer 32 is bonded to the radiation surface of the vibration part 41B (i.e., the lower surface of the vibration part 41B in FIG. 9). The area of ​​the bonding region of the acoustic matching layer 32 is set to be slightly smaller than the area of ​​the radiation surface. A step portion 88 is formed at a portion of the outer edge of the radiation surface where the acoustic matching layer 32 is not present. A front electrode 33 is formed as an electrode on the surface of this step portion 88. That is, the front electrode 33 formed on the piezoelectric element 31B is partially exposed at the step portion 88, and this portion is a connectable portion of the front electrode 33. Moreover, wiring is connected to this connectable portion by soldering or the like. The wiring here refers to an electric wire (not shown) that connects the front electrodes 33 of the vibration parts to each other, a first lead wire 51, and the like.

[0060] Next, a method for manufacturing the ultrasonic transducer 11A will be described with reference to FIG.

[0061] First, a rectangular flat ceramic sintered body 91 and an acoustic matching layer 32 also having a rectangular flat plate shape are prepared (preparation step). At this time, the acoustic matching layer 32 is selected to be one size smaller than the piezoelectric element 31B. Specifically, the acoustic matching layer 32 is prepared such that the length in the long side direction is almost equal to the length in the long side direction of the ceramic sintered body 91 and the length in the short side direction is slightly shorter than the length in the short side direction of the ceramic sintered body 91. In manufacturing the piezoelectric element 31B, first, a ceramic sintered body 91 made of lead zirconate titanate (PZT) is produced and its surface is polished. Next, metal layers that become the front side electrode 33 and the back side electrode 34 are formed on both main surfaces 42, and a process of applying a voltage to both electrodes 33 and 34 to polarize them is performed. Next, the acoustic matching layer 32 is bonded to the first surface 31a side of the piezoelectric element 31 (see FIG. 11(a)). At this time, a step 88 having a width of about 1 to 3 mm is formed in a portion where the acoustic matching layer 32 is not present on the outer edge of the front surface, which is the radiation surface.

[0062] Next, the ceramic sintered body 91 to which the acoustic matching layer 32 is bonded is set in a conventionally known cutting device and cut along two predetermined directions to form a plurality of vibration parts 41B having a substantially isosceles triangular shape in a plan view (cutting step). Specifically, in this cutting step, the ceramic sintered body 91 is first cut at equal intervals along a first direction D1 (see cutting line 92 in FIG. 11(b)). The first direction D1 refers to a direction that forms an angle (i.e., 10°) that is half the angle of the most acute interior angle (acute angle portion 72) with respect to the short side 91a of the ceramic sintered body 91. Next, the ceramic sintered body 91 is cut at equal intervals along a second direction D2 (see cutting line 93 in FIG. 11(c)). The second direction D2 refers to a direction that forms an angle (i.e., 20°) with the first direction D1 that is equal to the angle of the most acute interior angle (acute angle portion 72). By carrying out such cutting, a plurality of vibration parts 41B each having a substantially isosceles triangular shape as shown in FIG. 11(d) are formed.

[0063] Next, 18 of the cut out individual piezoelectric element pieces (i.e., vibration parts 41B with acoustic matching layers 32) are arranged so as to be rotationally symmetrical with the acute angle parts 72 facing the element center, to form the piezoelectric elements 31B (vibration part arrangement process). Specifically, as shown in Fig. 9, the vibration parts 41B with acoustic matching layers 32 are arranged on the inner surface 23a of the support plate 23, separated by the groove parts 36. At this time, the groove parts 36 are arranged so as to be mutually connected at the center of the piezoelectric element 31 and the support plate 23 and extend radially. In this arrangement, each vibration part 41B is adhesively fixed to the inner surface 23a of the support plate 23 via the acoustic matching layer 32.

[0064] Next, the first lead wire 51 and the second lead wire 52 are soldered to the front electrode 33 (i.e., the electrode formed in the step portion 88) and the back electrode 34 of the piezoelectric element 31, respectively (wiring connection process). Then, the wiring cable 53 is pulled out of the housing container 21 through the cable insertion hole 54, and the support plate 23 is placed and fixed on the front side 26 of the container body 22. As a result, the opening of the container body 22 is closed, and the piezoelectric element 31B is housed in the space within the housing container 21. Thereafter, the filler 38 is filled through a hole (not shown) provided in the housing container 21, and the space is filled with the filler 38 and molded integrally. In this manner, the ultrasonic transducer 11A is completed.

[0065] As described above, according to this embodiment, it is possible to obtain the ultrasonic transducer 11A for a measuring instrument that can widen the frequency band suitable for transmitting and receiving ultrasonic waves. In addition, the manufacturing method of this embodiment has the following advantages.

[0066] For example, when it is desired to obtain a plurality of vibration parts 41B having a substantially isosceles triangular shape as shown in FIG. 11(d), a circular ceramic sintered body is usually first produced. Then, it is necessary to cut it radially and then reshape it into a substantially isosceles triangular shape. However, this procedure has the disadvantage that a lot of material is likely to be wasted. In addition, when cutting the circular ceramic sintered body with a cutting device, it is necessary to rotate the ceramic sintered body and determine the cutting direction at least nine times, which is a complicated operation. Moreover, in this case, it is necessary to accurately position and fix the center of the circular ceramic sintered body to the cutting device, and if this fixing is not possible, it is difficult to obtain the vibration part 41B of the desired shape.

[0067] In contrast, according to the manufacturing method of this embodiment, the rectangular flat ceramic sintered body 91 is basically cut in two directions D1 and D2, so the work is not complicated and the vibration part 41B of the desired shape can be obtained relatively easily. Also, the amount of cut-off parts can be reduced.

[0068] As described above, according to the manufacturing method of this embodiment, the wideband ultrasonic transducer 11A can be manufactured relatively simply and efficiently while reducing waste of materials.

[0069] [Third embodiment] A method for manufacturing an ultrasonic transducer 11A according to a third embodiment of the present invention will be described below with reference to Figures 12 and 13. Here, the following description will focus on the differences from the first and second embodiments, and common parts will be given the same reference numerals and will not be described in detail.

[0070] As shown in Fig. 12, the piezoelectric element 31C in the ultrasonic transducer 11A of the third embodiment is a ceramic plate-like object having a substantially circular outer shape, and includes 18 vibration parts 41C each having an elongated substantially right-angled triangular shape in a plan view. In each vibration part 41, one interior angle, which is the most acute angle, is 20°, and the other two interior angles are 80°. As shown in Figs. 11 and 12, the interior angles (acute angle parts 72), which are the most acute angles in each vibration part 41C, are located on the central side of the piezoelectric element 31C, and are all chamfered to prevent chipping.

[0071] Next, a method for manufacturing this ultrasonic transducer 11A (mainly a method for producing the piezoelectric element 31C) will be described with reference to FIG.

[0072] First, the same rectangular plate-shaped ceramic sintered body 91 as in the third embodiment and the acoustic matching layer 32 also having a rectangular plate-shaped configuration are prepared (preparation step, see FIG. 13(a)).

[0073] Next, the ceramic sintered body 91 to which the acoustic matching layer 32 is bonded is set in a cutting device and cut along two predetermined directions to form a plurality of vibration parts 41C having a substantially right-angled triangular shape in a plan view (cutting step). Specifically, in this cutting step, the ceramic sintered body 91 is first cut along a first direction D1 at equal intervals (see cutting line 92 in FIG. 13(b)). The first direction D1 refers to a direction parallel to the short side 91a of the ceramic sintered body 91. Next, the ceramic sintered body 91 is cut along a second direction D2 at equal intervals (see cutting line 93 in FIG. 13(c)). The second direction D2 refers to a direction that forms an angle (i.e., 20°) with the first direction D1 equal to the angle of the acutest interior angle (acute angle part 72). Then, by performing such cutting, a plurality of vibration parts 41C having a substantially right-angled triangular shape as shown in FIG. 13(d) is formed.

[0074] Next, 18 of the cut out individual piezoelectric element pieces (i.e., vibration parts 41B with acoustic matching layer 32) are used and arranged so that the acute angle parts 72 are rotationally symmetrical toward the element center to form piezoelectric element 31C (vibration part arrangement process). Thereafter, a wiring connection process is performed, and then resin molding is performed to complete ultrasonic transducer 11A. Even with the manufacturing method of this embodiment, the above-mentioned wideband ultrasonic transducer 11A can be manufactured relatively simply and efficiently while reducing waste of material. It should be noted that the manufacturing method of this embodiment can greatly reduce waste of material.

[0075] [Fourth embodiment] An ultrasonic transducer 11D according to a fourth embodiment of the present invention will be described below with reference to Figures 14 to 16. Here, the following description will focus on the differences from the first embodiment and the like, and common parts will be given the same reference numerals and will not be described in detail.

[0076] As shown in FIG. 14, the ultrasonic transducer 11D of the fourth embodiment has a different configuration of the support plate 23A from the support plate 23 of the first embodiment. That is, the support plate 23 of the first embodiment has a flat surface shape, but the support plate 23A of this embodiment has a non-flat surface shape. Specifically, the support plate 23A has a surface shape corresponding to the pyramidal surface of an octagonal truncated pyramid, and is generally convex toward the outer surface 23b side of the support plate 23A and generally concave toward the inner surface 23a side. That is, in the case of the support plate 23D, the pyramidal surface of the polygonal truncated pyramid has constituent surfaces of the same number (i.e., 18) as the division number n of the piezoelectric element 31D (see FIG. 16). All of the 18 constituent surfaces are substantially isosceles triangular (isosceles triangular with the acute angle portion 72 chamfered). Then, on the opposite side of each component surface (more precisely, on the inner surface of the support plate 23A), a vibration section 41B that is one size smaller than the component surface is adhered and fixed one by one via an acoustic matching layer 32. Here, the angle that the inner surface 23a of the support plate 23A, which is the vibration section support surface, makes with the plane perpendicular to the central axis of the ultrasonic transducer 11D is defined as the inclination angle θ. The inclination angle θ is not particularly limited and can be set arbitrarily, but is set, for example, to about 5° to 60°, and preferably to about 10° to 60°.

[0077] According to the fourth embodiment configured as above, in addition to the effects of the first embodiment, the following effects can be achieved. That is, the support surface of the support plate 23A has a surface shape corresponding to the pyramidal surface of a frustum of a polygonal pyramid, and is generally convex toward the outer surface side of the support plate 23A. With this configuration, each vibration part 41B can be stably supported on the support plate 23A while being held at a desired angle (15° in this case). Furthermore, the directivity angle can be made wider than when the piezoelectric element 31 is supported on the support plate 23 having a flat surface shape. Incidentally, it is also possible to select a support plate whose support surface has a curved surface shape corresponding to the conical surface of a cone or a frustum of a cone, and to support each vibration part 41 on it. However, with this configuration, since each vibration part 41 is bonded to a curved surface, it is difficult to stably support each vibration part 41 on the support plate, and a gap is likely to be formed between the support plate and the vibration part 41. In addition, it is also difficult to position each vibration part 41 with respect to the support plate. In this respect, the support plate 23A as in this embodiment is preferable in that the above problem is unlikely to occur.

[0078] [Fifth embodiment] A fifth embodiment of the present invention will be described below with reference to Figures 17 and 18. Here, the description will focus on the parts that are different from the first and fourth embodiments, and the same parts will be given the same reference numbers and detailed descriptions will be omitted.

[0079] As shown in FIG. 17, the ultrasonic transducer 11E of the fifth embodiment differs from the support plate 23A of the fourth embodiment in that the support plate 23B is generally concave toward the outer surface 23b and generally convex toward the inner surface 23a. The support plate 23B has a pyramidal surface of a frustum of a polygonal pyramid with a number of constituent surfaces equal to the number n of divisions of the piezoelectric element 31E (i.e., 18). A vibration part 41B that is one size smaller than the pyramidal surface is bonded and fixed one by one to each constituent surface via an acoustic matching layer 32. The inclination angle θ of the support plate 23B is not particularly limited and can be set arbitrarily, and is set to, for example, about 5° to 60°. In this embodiment, the inclination angle θ of the inner surface 23a of the support plate 23B is 15°, so that each vibration part 41B is supported by the inner surface 23a of the support plate 23B at an angle of 15° with respect to the plane perpendicular to the central axis. FIG. 18 shows the piezoelectric element 31E in a state in which the vibration portions 41B are arranged at an inclination angle θ of 15°.

[0080] According to the fifth embodiment configured as above, in addition to the effects of the first embodiment, the following effects can be achieved. That is, the support surface of the support plate 23B has a surface shape corresponding to the pyramidal surface of a polygonal frustum, and is generally concave toward the outer surface 23b side of the support plate 23B. With this configuration, each vibration part 41B can be stably supported on the support plate 23B while being held at a desired angle (15° in this case). Furthermore, the directivity angle can be narrowed compared to the case where the piezoelectric element 31 is supported on the support plate 23 having a flat surface shape. Also, as in the fourth embodiment, no gap is formed between the support plate and the vibration part 41B, and the positioning of each vibration part 41B with respect to the support plate can be easily performed.

[0081] The above embodiment may be modified as follows.

[0082] In the above embodiments, the vibration parts 41, 41A, 41B, and 41C are supported and fixed to the support plates 23, 23A, and 23B located on the front side 26 of the housing receptacle 21. However, the present invention is not limited to this. For example, the vibration parts 41, 41A, 41B, and 41C may be supported and fixed to a support plate located on the rear side 27 of the housing receptacle 21.

[0083] The piezoelectric elements 31, 31A to 31F in the above embodiments are configured using 24 vibration parts (central angle 15°) or 18 vibration parts (central angle 20°). However, the piezoelectric elements 31, 31A to 31F may be configured using 25 or more (e.g., 30, 36, etc.) vibration parts, or 23 or less (e.g., 16, 12, 10, 8, etc.) vibration parts. In the above embodiments, the piezoelectric elements 31, 31A to 31F have vibration parts with the same central angle, but the piezoelectric elements 31, 31A to 31F may have multiple types of vibration parts with different central angles.

[0084] In the ultrasonic transducers 11, 11A, 11D, and 11E of the above embodiments, the grooves 36 between the vibration parts 41 are generally voids, but the voids may be filled with a filler 38 (fixing member). When the filler 38 is used, the adjacent vibration parts 41 can be joined and fixed to each other by the hardened filler 38. In this case, the specific gravity of the filler 38 is not particularly limited, but is preferably 1.5 or less, for example. In this way, the filler 38 becomes relatively light, so that the filler 38 is less likely to become a load when the vibration part 41 vibrates. As a result, it is possible to prevent a decrease in transmission and reception sensitivity caused by the use of the filler 38.

[0085] A soundproofing material such as sponge may be placed in the gaps of the grooves 36 between the vibrating parts 41 as a fixing member in place of the filler 38. Specifically, as in another embodiment of a piezoelectric element 31F shown in Fig. 19, a soundproofing sheet 81 with double-sided tape 82 may be placed between adjacent vibrating parts 41. In this case, it is preferable that the double-sided tape 82 is provided on both sides of the soundproofing sheet 81. The double-sided tape 82 of the soundproofing sheet 81 can be attached to the side surface S1 of the vibrating part 41. Therefore, when this is used, the vibrating parts 41 can be joined and fixed to each other reliably and relatively easily with each of them correctly positioned.

[0086] The piezoelectric element 31F having the above-mentioned tape-attached structure may be supported and fixed to the support plate 23, 23A, 23B as in the above-mentioned embodiments, but it is not necessary. For example, it may be structured as an ultrasonic transducer 11F of another embodiment shown in FIG. 20. This ultrasonic transducer 11F uses a housing container 21 having rod-shaped or protruding supports 85 provided at multiple locations on the inner wall. The piezoelectric element 31B having the above-mentioned tape-attached structure is accommodated in this housing container 21, and is supported at the tip of the support 85, thereby determining the posture of the piezoelectric element 31B. In this state, the piezoelectric element 31B is molded by the filler 38.

[0087] The vibration parts 41 are joined and fixed to each other in a state where they form the same inclination angle θ with respect to a plane perpendicular to the central axis of the piezoelectric element 31B. For example, when a soundproofing sheet 81 having a uniform thickness (in other words, two side surfaces S1 are parallel) is used as shown in FIG. 19, the piezoelectric element 31B can be configured in a flat state (i.e., inclination angle = 0°) where the bottom surface of each vibration part 41 is located in one plane. When a soundproofing sheet 81 having an uneven thickness different in the vertical direction is used, each vibration part 41 can be arranged at an incline. Specifically, for example, when a soundproofing sheet 81 having a thickness that increases downward is used, each vibration part 41 can be arranged at an incline with the center of the piezoelectric element 31B being convex toward the first surface 31a. Conversely, when a soundproofing sheet 81 having a thickness that decreases downward is used, each vibration part 41 can be arranged at an incline with the center of the piezoelectric element 31B being concave toward the first surface 31a.

[0088] In the ultrasonic transducers 11, 11A, 11D, 11E, and 11F of the above-described embodiments, the piezoelectric elements 31, 31A to 31F made of lead zirconate titanate (PZT) are used, but the material for forming the piezoelectric elements 31, 31A to 31F is not particularly limited. For example, potassium sodium niobate (alkali niobate), barium titanate, PMN-PT(Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3) single crystal, PZNT(Pb(Zn 1 / 3 Nb2 / 3 Alternatively, a piezoelectric element made of piezoelectric ceramics such as a single crystal of PbTiO3 or a single crystal of LiNbO3 may be used.

[0089] In the above embodiments, the ultrasonic transducers 11, 11A, 11D, 11E, and 11F are used as ultrasonic transducers for a fish finder, but the present invention is not limited to this and may be used in other measuring devices. For example, the ultrasonic transducers 11, 11A, 11D, 11E, and 11F may be used in sonar that electrically or mechanically changes the direction of ultrasonic wave irradiation, as well as in measuring devices such as sounders that measure water depths and airborne sensors that measure distances in the air. [Explanation of symbols]

[0090] 11, 11A, 11D, 11E, 11F...Ultrasonic transducers for measuring instruments 21…Housing container 23, 23A, 23B...Support plate as a support 23a...(Inner surface of support plate) 23b...Outer surface (of support plate) 26...Front side (of the housing) 27...Rear side (of the housing) 31, 31A, 31B, 31C, 31D, 31F...Piezoelectric element 31a…First page 31b…Second side 32...Acoustic matching layer 33...Front electrode as electrode 38...Filling material 41, 41A, 41B, 41C... Vibration part 72...Acute angle 81...Soundproofing sheet 82…Double-sided tape 85...Support 88…Step 91...Sintered ceramic A3…Thickness direction A4…Radial direction D1…First direction D2…Second direction L1: Thickness of the vibrating part L2: Width of vibrating part L3: Radial length of the vibrating part θ…Inclination angle

Claims

1. An ultrasonic transducer for a measuring instrument that transmits and receives ultrasonic waves, A housing container having a support; A piezoelectric element having a substantially circular outer shape and supported by the support; Equipped with the piezoelectric element is configured to include eight or more vibration parts that are arranged in a rotational symmetry manner with one interior angle of 45° or less and the other two interior angles of 45° or more in a substantially acute triangle shape in a plan view, with the acutest interior angle facing the center of the element; The piezoelectric element vibrates in a thickness direction at a first frequency band and vibrates in a radial direction at a second frequency band lower than the first frequency band.

1. An ultrasonic transducer for use in a measuring instrument, comprising:

2. 2. The ultrasonic transducer for a measuring instrument according to claim 1, wherein the support body is a support plate having a flat surface shape.

3. 2. The ultrasonic transducer for a measuring instrument according to claim 1, wherein the support body is a support plate having a surface shape corresponding to a pyramidal surface of an approximately polygonal pyramid or an approximately frustum of a polygonal pyramid, and which is generally convex on its outer surface.

4. 2. The ultrasonic transducer for a measuring instrument according to claim 1, wherein the support body is a support plate having a surface shape corresponding to a pyramidal surface of an approximately polygonal pyramid or an approximately polygonal truncated pyramid, and which is generally concave on its outer surface.

5. 5. The ultrasonic transducer for a measuring instrument according to claim 3, wherein the plurality of vibration parts are supported by a plurality of constituent faces that constitute the pyramidal surface, respectively.

6. 5. The ultrasonic transducer for a measuring instrument according to claim 1, wherein the thickness of the vibrating part is greater than the width of the vibrating part, and the length of the vibrating part in the centrifugal direction is three times or more the thickness of the vibrating part.

7. 5. The ultrasonic transducer for a measuring instrument according to claim 1, wherein a portion of said vibration portion corresponding to said interior angle that is the acutest angle is chamfered.

8. an acoustic matching layer having an area smaller than that of the vibration section is bonded to the radiation surface of the vibration section; an acoustic matching layer is bonded to the radiation surface of the vibration section, and an area of ​​a bonding region of the acoustic matching layer is set to be smaller than an area of ​​the radiation surface; a step portion is formed at a portion of the outer edge of the radiation surface where the acoustic matching layer is not present, An electrode is formed on the step portion.

5. An ultrasonic transducer for use in a measuring instrument according to claim 1.

9. 5. The ultrasonic transducer for a measuring instrument according to claim 1, wherein adjacent ones of the vibration sections are joined and fixed to each other by a soundproof sheet with double-sided tape.

10. A method for manufacturing an ultrasonic transducer comprising: a housing container having a support; and a piezoelectric element having a substantially circular outer shape and supported by the support, the piezoelectric element including eight or more vibrating parts that form a substantially acute triangle shape in a plan view with one interior angle of 45° or less and two other interior angles of 45° or more, and that are rotationally symmetrically arranged with the acutest interior angle toward the center of the element, the piezoelectric element vibrating in a thickness direction in a first frequency band and vibrating in a radial direction in a second frequency band lower than the first frequency band, A preparation step of preparing a rectangular flat ceramic sintered body; a cutting process for cutting the ceramic sintered body at equal intervals along a first direction and at equal intervals along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming a plurality of the vibration parts each having a substantially acute triangle shape; a vibration part arrangement process for forming the piezoelectric element by arranging eight or more of the obtained vibration parts so that the acutest interior angle is rotationally symmetric toward the element center; A method for manufacturing an ultrasonic transducer for a measuring instrument, comprising:

11. The plurality of vibration portions are generally right-angled triangular in plan view, In the cutting step, the ceramic sintered body is cut at equal pitches along the first direction parallel to the short side of the ceramic sintered body, and cut at equal pitches along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming a plurality of the vibration parts each having a substantially right-angled triangular shape. The method for manufacturing an ultrasonic transducer for a measuring instrument according to claim 10.

12. The plurality of vibration parts are generally isosceles triangular in plan view, 11. The method for manufacturing an ultrasonic transducer for a measuring instrument according to claim 10, wherein in the cutting step, the ceramic sintered body is cut at equal pitches along the first direction that forms an angle of half the acutest interior angle with respect to a short side of the ceramic sintered body, and cut at equal pitches along a second direction that forms an angle equal to the acutest interior angle with the first direction, thereby forming a plurality of the vibration parts each having a substantially isosceles triangular shape.

13. a piezoelectric element having a substantially circular outer shape and supported by the support, the piezoelectric element including eight or more vibration sections that form a substantially acute triangle shape in a plan view with one interior angle of 45° or less and two other interior angles of 45° or more, the acutest interior angle being rotationally symmetrically arranged toward the center of the element, an acoustic matching layer is bonded to a radiation surface of the vibration section, and an area of ​​a bonding region of the acoustic matching layer is set to be smaller than an area of ​​the radiation surface, a step section is formed at a location on the outer edge of the radiation surface where the acoustic matching layer is not present, and an electrode is formed on the step section, the piezoelectric element vibrates in a thickness direction in a first frequency band and vibrates in a radial direction in a second frequency band lower than the first frequency band, a preparation step of preparing a rectangular flat-plate shaped ceramic sintered body having a rectangular flat-plate shaped acoustic matching layer, the rectangular flat-plate shaped acoustic matching layer being one size smaller than the rectangular flat-plate shaped ceramic sintered body, bonded to one side of the ceramic sintered body; a cutting process for cutting the ceramic sintered body at equal intervals along a first direction and at equal intervals along a second direction that forms an angle with the first direction equal to the acutest interior angle, thereby forming a plurality of the vibration parts each having a substantially acute triangle shape; a vibration part arrangement process for forming the piezoelectric element by arranging eight or more of the obtained vibration parts so that the acutest interior angle is rotationally symmetric toward the element center; a wiring connection step of connecting wiring to the electrode formed on the step portion of the vibration portion; A method for manufacturing an ultrasonic transducer for a measuring instrument, comprising:

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